package org.bouncycastle.asn1;

import java.io.IOException;
import java.math.BigInteger;

public class DERInteger extends ASN1Object {
    byte[] bytes;

    /**
     * return an integer from the passed in object
     * 
     * @exception IllegalArgumentException
     *                if the object cannot be converted.
     */
    public static DERInteger getInstance(Object obj) {
        if (obj == null || obj instanceof DERInteger) {
            return (DERInteger) obj;
        }

        if (obj instanceof ASN1OctetString) {
            return new DERInteger(((ASN1OctetString) obj).getOctets());
        }

        if (obj instanceof ASN1TaggedObject) {
            return getInstance(((ASN1TaggedObject) obj).getObject());
        }

        throw new IllegalArgumentException("illegal object in getInstance: " + obj.getClass().getName());
    }

    /**
     * return an Integer from a tagged object.
     * 
     * @param obj
     *            the tagged object holding the object we want
     * @param explicit
     *            true if the object is meant to be explicitly tagged false otherwise.
     * @exception IllegalArgumentException
     *                if the tagged object cannot be converted.
     */
    public static DERInteger getInstance(ASN1TaggedObject obj, boolean explicit) {
        return getInstance(obj.getObject());
    }

    public DERInteger(int value) {
        bytes = BigInteger.valueOf(value).toByteArray();
    }

    public DERInteger(BigInteger value) {
        bytes = value.toByteArray();
    }

    public DERInteger(byte[] bytes) {
        this.bytes = bytes;
    }

    public BigInteger getValue() {
        return new BigInteger(bytes);
    }

    /**
     * in some cases positive values get crammed into a space, that's not quite big enough...
     */
    public BigInteger getPositiveValue() {
        return new BigInteger(1, bytes);
    }

    void encode(DEROutputStream out) throws IOException {
        out.writeEncoded(INTEGER, bytes);
    }

    public int hashCode() {
        int value = 0;

        for (int i = 0; i != bytes.length; i++) {
            value ^= (bytes[i] & 0xff) << (i % 4);
        }

        return value;
    }

    boolean asn1Equals(DERObject o) {
        if (!(o instanceof DERInteger)) {
            return false;
        }

        DERInteger other = (DERInteger) o;

        if (bytes.length != other.bytes.length) {
            return false;
        }

        for (int i = 0; i != bytes.length; i++) {
            if (bytes[i] != other.bytes[i]) {
                return false;
            }
        }

        return true;
    }

    public String toString() {
        return getValue().toString();
    }
}
